elite7

I use 93 octane around here.

ippo

In Holland we have 95 octane and premium is 98. In Germany they have even 100

fensterlip

Octane is measured with 2 scales. There is the "Research Octane" number and the "Motor Octane" number. Research numbers are 20% or so higher. In the States they average the 2 numbers to give the octane number. This can account for differences. The poor mileage is probably the fuel after all the changes you have done.
In California they mandate a special formulation that is supposed to minimize emissions. Well, it minimizes the miles per gallon I can affirm. In Texas, New Mexico and Arizona I get 28 mpg on the highway and Cali gas makes it a prompt 26 mpg. Your numbers are remarkably low however. Can you get a "special fuel" somewhere to test with?

F16uae

Yo dude thats the exact same gas mileage that i get on my 01 !! Is your problem fixed now ? If so then how ??

Johnhav430

Again I think I am not allowed to mention other brands of motor vehicles, but also I'm always surprised that science today is discounted as it is. Just look at the virus. Anyway, it would be fascinating to put various octanes in when people didn't know what they were, and have them return their results. Meaning we give you free gasoline, but we're not telling you if it's 87, 89, 91, 93, 94, 97, and have you keep a log. And we switch it up, it's never the same fill up to fill up. I have a funny feeling there will be no correlation between the log, and the octane. my .02.

What I'm driving at is octane has a specific, scientific, meaning.

Striker223

And if you knew how this engine advances spark and it's low RPM cylinder pressure management tactics you would understand why 91-93 gets more MPG. It can't run at it's desired cylinder pressure on 87 and thus doesn't get the same amount of work done at low rpm that people normally drive at.